Post-asphyxia perinatal brain injury is a leading cause of neonatal encephalopathy, a serious healthcare problem. Cerebral vascular dysfunction may lead to adverse neurological sequelae. This proposal is designed to provide new understanding of perinatal asphyxia-induced cerebral vascular dysfunction, endogenous protection, and outline potential approaches for intervention. The proposal is built on our previous accomplishments of discovering hydrogen sulfide (H2S) as a critical component of regulation of newborn cerebral blood flow regulation. The proposed experiments are novel, critically important and have direct applicability to a devastating pathological condition. Preliminary data suggest H2S formed by endothelial cystathionine-?-lyase (CSE) provides protection from asphyxia-induced cerebral vascular damage. The research proposed pursues the unifying hypothesis that, in newborn brain, asphyxia disrupts vascular H2S signaling and cerebral arteriolar smooth muscle KATP and/or BKCa channel activity causing cerebrovascular dysfunction, while elevation of H2S limits the dysfunction. To test this hypothesis, four specific hypotheses will be tested using a novel asphyxia model in newborn pigs: 1. Asphyxia injures cerebrovascular endothelial cells causing loss of H2S-mediated pial arteriole dilation. 2. Asphyxia reduces H2S-induced Ca spark and BKCa 2+ channel activation, and vasodilation. 3. Asphyxia inhibits H2S-induced KATP channel activation and vasodilation. 4. H2S reduces asphyxia-induced ROS and post-asphyxia vascular dysfunction. A multi system approach combining in vivo and in vitro techniques is unique and advantageous to uncover mechanisms responsible for cerebral vascular dysfunction. Cranial windows allow observation of the microcirculation, collection of cortical CSF and topical application of agonists, precursors and inhibitors. H2S production in vivo and in vitro is identified and quantified by gas chromatography-mass spectrometry and a selective electrode. Cerebral arterioles, and endothelial and smooth muscle cells from control and post-asphyxia brains allow study of H2S production, arteriolar reactivity, and vascular smooth muscle function. Patch clamp techniques will be used to examine BKCa channel activity. Global cytosolic Ca and Ca sparks in intact arterioles and VSM will be studied 2+ 2+ using fluorescent indicator technology with a dual excitation, single emission system and laser scanning confocal microscopy, respectively. Importantly, experimental interventions that may attenuate cerebrovascular malfunction caused by asphyxia are examined. The research proposed is highly significant in addressing a major cause of perinatal morbidity and mortality in a manner that could result in new approaches for prevention and treatment of post-asphyxia perinatal brain injury, a serious healthcare problem both in cost and lifelong disabilities.